For those running E85 fuel,
do you see more, less, or the same amount of
carbon deposits
inside the combustion chamber,
on the piston crown
or on the spark plugs?

btt

Since I added 30% E-85 to my '69 440 10:1 engine
I'm able to add 5 degrees more timing with no ping. I also used E-85 in my '81 Kawasaki 440 8:1
motor and it stopped the pinging that it has had since day 1, even though I use 93 octane. No timing change. Finally I used it in my 25 year old
Briggs & Stratton with no ill effects.
Can't say about the carbon deposits but I would ask the guys in Race Only. E-85

Did you have to change much to run the E85 blended with your unleaded?

I did not change anything. E-85 is 105 octane.

It tends to clean out carbon and leaves very little of its own. After running e-85 in my cuda with no changes at all it cleaned the soot out of the exhaust pipes.